Writing is not hard. What is hard, and what trips most people up when they are writing, is organization. When you want to write clearly, it is important to have a clear idea of what you are going to say. Before you begin, think about your idea. You can think about it with a pen and paper or a word processor, if that helps you to work better. Make a list, jot down words that you could use, outline your article. You are about to present your idea to the world — give it a fighting chance by working through your argument. Think about the timeline of the piece and how it should flow.
For example, if your subject is a person and you want to write about their life, say a profile for a website or magazine or some such, you may have a questionnaire they have filled out. Put the pertinent information in the same document where you are going to write, and check off the important points as you accomplish them. Keeping track of what you need to cover will help you stay on track if you veer off onto a side issue.
You can also refer back to the list after your first draft, to see whether you have gone too far in any direction, and need to prune your piece. Perhaps that extra paragraph is the seed for next week! GoogleDocs is my favorite place to write, because of the complete accessibility from any location and the easy cut and paste and save if I need to put an idea somewhere else. Also, I appreciate the auto-save. Can’t tell you how many times I’ve nearly lost several hours worth of work …
If you’re not in a place where you can write, but you have a great idea, put it on paper or save it in an email to yourself, just a basic sentence and perhaps one or two theme words. You can continue to think about it as you go about your business; I often find that percolation is the best possible thing for an idea that needs to be fleshed out.